[Bug c++/80635] std::optional and bogus -Wmaybe-uninitialized warning

[palves at redhat dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80635

--- Comment #9 from Pedro Alves <palves at redhat dot com> ---
> So maybe we just want to use a #pragma around the std::optional destructor to suppress this warning.

I had tried that last night, but unfortunately it couldn't get it to work,
because the warning triggers in A, not optional<A>.  Users of optional<T> have
to put the #pragma around their the Ts (in this case A::~A()).  I.e., this
would work:

 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wmaybe-uninitialized"

 struct A
 {
   A () : m (get ()) {}
   ~A () { set (m); }  // warns here

   int m;
 };

 #pragma GCC diagnostic pop

I think as we'll use gdb/std::optional more and more, that would become too
unwildy/ugly.  My current workaround in gdb is -Wno-error=maybe-uninitialized:

[1] - https://sourceware.org/ml/gdb-patches/2017-05/msg00130.html